Aluminum alloy



v of the alloys do not materially .25

Patented May 23, 1933 UNITED STATES PATENT, OFFICE FRED KELLER AND CHARLES M. CRAIGHEAD, OF KENSINGTON, PENNSYLVANIA,

ASSIGNOBS TO ALUMINUM COMPANY OF AMERIOA, OF PITTSBURGH, PENNSYL- VANIA, A CORPORATION OF PENNSYLVANIA r ALUMI'N'UI ALLOY No Drawing. Original application filed November 30, 1932, Serial No. 845,127. Divided and this applicatioufiled February 15, 1933. 7 Serial No. 856,952.

This invention relates to aluminum base alloys which are possessed of high tens1le properties, excellent resistance to corrosion, and the further property of retaining a substantial part of their original surface appearance after continued exposure to the atmosphere. I

There are uses of aluminum base alloys where high strength, good corrosion-resistance and good appearance are primary 1' uisites. Exemplary of such uses are win ow frames. Such frames are often built up from extruded or rolled aluminum base alloy shapes. Since the distinctive color of aluminum lends itself readily to modern,design, aluminum base alloys which will retain their natural color and appearance un-' der constant exposure to ordinary or industrial atmospheres are in great demand. The alloys must also, ifadaptable to such uses, be of high strength and must likewise be resistant to corrosion in the sense that upon long exposure the tensile roperties epreciate. The known high strength aluminum base al-. loys have,'more or less, fulfilled the abovenoted requirements, but there has been a need for an alloy which would combine, to a larger extent, high strength, corrosionresistance and a stable surface appearance. It is the general object of this inventionto provide alloys of this nature.

Among the high strength aluminum base alloys which are best adapted to the uses and purposes abovementioned are the alloys described in the United States Patent No. 1,472,739 to Robert S. Archer and Zay Jeffries. The alloys described in this patent are characterized by the simultaneous presence therein of magnesium and siliconand primarily derive their good tensile properties from the action and efiect of these all loying elements under the influence of heattreatment and artificial aging. When magnesium and silicon are together present in aluminum, they form a complex which is usually recognized as the intermetallic compound, Mg Si. lhe com ound is to a certain extent soluble in t e aluminum. When aluminum containing this compound is thermally treated at temperatures above about 500 'centrigrade but below the temperature at which incipient fusion takes place in the allo a portion of the Mg si forms a solid so ution with 'the aluminum, increasing the strength of that metal. If the alloy is then cooled more or less rapidly and thereafter artificially aged by heating to temperatures of about 100 to 200 centigrade, the strength of the alloy is further increased.

In experimenting with this general type of aluminum base alloywe have discovered certain alloyswhich are generally superior thereto. We have discovered that if an alloy of high tensile properties, excellent corrosion-resistance and stable surface a pearance is desired, the best combination 0 these properties can be obtained when neither an excess of magnesium nor an excess of silicon is present in the alloy, but that the magnesium and silicon should be present in such amounts as will combine substantially completely to form the intermetallic compound Mg S1. Furthermore, as we have discovered, the alloy should contain from 0.1 to 1.0 per cent by weight in total of one or more of the class of metals herein defined to be chrrr mium, manganese, molybdenum, tungsten,

vanadium, zirconium, titanium, and uranium. This class of elements'has two com:

.mon properties, one being the hardening of the aluminum with which they are mixed; and the other being the fact that in our novel alloys they achieve their stated purpose without in uring the other desirable properties of the alloy. Likewise they cooperate jointly or severally, as the case may be, to produce the novel composition the properties of which are herein described. One or more of these metals may be present in the alloy but they should not exceed in total the limits of 0.1 to 1.0 per cent by weight. When the elements are used singly in the alloy the chromium should. not exceed 0.1 to 1.0 per cent by weight, the manganese should not exceed'0.1 to 1.0 per cent by weight, the molybdenum should not exceed 0.1 to 1.0 per cent by weight, the tungsten should not exceed 0.1 to 0.5 per cent by weight, and vanadium should not exceed 0.1 to 1.0 per centbalance being by Weight, the zirconium should not exceed 0.1 to 1.0 per cent by weight, the titanium should not exceed 0.1-to 0.5 per cent by weight, and the uranium should not exceed 0.1 to 1.0 per cent by weight. The aluminum from which the alloy is compounded should not contain more than 0.3 per cent by weight of impurities, said amount of impurities, of course, being exclusive of magnesium, silicon, and the elements of the class above named.

The alloys contemplated by our invention are those which contain about 0.5 to 3.0 per cent by weight of Mg Si (or magnesium and silicon in amount and ratio to form such amounts of Mg si), which contain no'substantial excess of magnesium orsilicon over the amounts necessary to form Mg Si and which contain 0.1 to 1.0 per cent in total of at least one of the elements chromium, manganese, molybdenum, tungsten, vanadium, zirconium, titanium, and uranium, the balance of the alloy beingaluminum containing not more than 0.3' per cent by weight of impurities exclusive, of course, of silicon, magnesium, chromium, manganese, molybdenum, tungsten, vanadium, zirconium, titanium, and uranium. Alloys of this composition have tensile properties sufiiciently high to meet many engineering specifications. They have, moreover, an excellent corrosionresistance and stability of surface appearance. In this combination of properties they excel other high strength aluminum base alloys known and, in addition to these properties, alloys of thiscomposition are readily worked into usual and even intricate forms and shapes.

The alloys above described may be heattreated and aged and otherwise thermally treated according to the methods known to the art and may by means of the known methods of working be fabricated into many shapes. The alloys may likewise be cast according to usual foundry practices.

Of the alloys which are the subject of this invention certain are preferred, especially as material from which to formwindow frames and like articles. These are the alloys of higher strength which'still retain excellent workability. These alloys contain about 1.5 to 2.0 per cent bywcight of Mg Si, about 0.1 to 1.0'per cent by wei ht of at least one of the class of elements 0 iromium, manganese, molybdenum, tungsten, vanadium*, -zirconium, titanium, and uranium, and the balance being aluminum'containing hot more than about 0.3 per cent by weight of impurities exclusive of magnesium, silicon,

chromium, manganese, molybdenum, tungsten,'vanadium, zirconium, titanium, and

- uranium. -For example, alloys containing 1.5 to 2.0 per cent by weight of Mg Si, 0.1 to 1.5 per cent by weight of chrom um, the

aluminum of the purity above named, have, in extruded form and after heat-treatment at about 515 centigrade followed by cooling and artificial aging at about 160 centigrade for about 18 hours, an average tensile strength of 35,000 to 39,000 pounds per square inch, an average yield strength of 30,000 to 34,000 pounds per square inch, and an elongationof about 14 to 17 per cent in 2 inches. 1

It is a further beneficial property of the novel alloys herein described that they are, under the commercial methods of working and heat-treatment, singularly free from the phenomena of grain growth or large or uneven sized grains and that, partly because of this fact, they present in the Worked condition a surface which is even and smooth.

This application is a division of our copending application Serial No. 645,127, filed Nov. 30, 1932. y

We claim as our invention:

An alloy containing about 0.5 to 3.0 per cent by weight of the intermetallic com-' 

